As systems, such as computer systems, continue to evolve, the systems operate at increasingly higher speeds. As operating speeds increase, it is generally desired that the timing control signals communicated within the system improve in accuracy. Clock signals, which are employed to synchronize signals are generally designed to reach a destination device or location at the same time. Accordingly, the propagation delay time (i.e., the time it takes for each clock signal to travel along the respective transmission line) is calculated to synchronize the arrival of the clock signals at the destination device or location. Delay lines are typically used to assist in timing the transmission of clock signals between two points without generally requiring a large amount of physical space within the system or circuit being designed.
Typical embedded delay lines are routed through the base material (e.g. fiberglass or other insulator) between two reference planes held in a constant potential, for example, at ground. In such situations, the waves or signals produced are generally transverse electromagnetic (TEM) waves and the propagation delay is generally constant along a delay line irregardless of the geometry or positioning of the delay line between the reference planes. Since the geometry and positioning of the delay line does not substantially affect the propagation delay, the propagation delay along the delay line is primarily dependent upon the length of the delay line and the base material used.
However, the implementation of a propagation delay along calculated lengths of delay lines does not always produce actual results within the tolerances of high speed systems. In addition, the propagation delay of the embedded delay lines are not typically adjustable after the initial manufacture of a system including the delay line. As a result, delay line systems are often remanufactured with adjustments being made in an iterative process based on propagation delay testing until a desired propagation delay is achieved. In some instances, this process is both time consuming and expensive. In addition, systems and electronic component parameters can change over the manufacturing life of the system product, which in some circumstance may cause clock signals to be desynchronized.